MECH3460 Shaft Methodologies - Chain Drive Mixer Assignment 3

Introduction

Assignment 3 focuses on the use of two analysis methods in order to arrive at suitable design of a shaft to suit the chain drive to a mixer. The layout of the drive is shown pictorially on Figure 1.0 below and in the SALA catalogue (compare old and new), available on CANVAS. Note the use of a shaft mounted gearbox.

Operating Environment

It is intended to use an available appropriate synchronous motor rated to operate at 1440 rpm. The motor which weighs 40 kg will be directly coupled to the input shaft of the gearbox, (not using a belt drive as shown on Figure 1.0.) The output of the gearbox is to run at 100 rpm within about 5%. The pitch circle diameter of the chain sprocket is to be approximately 330 mm. The tension in the chain will vary with the volume and density of the material in the mixer drum used paper mill, but it has been determined that the highest tension will be 15.0 kN and that the high-tension leg of the chain will be within 15? of vertical. The movement of the material within the mixing drum will produce essentially no shock loads. The SALA catalogue also specifies other factors to be considered. This installation will be operated for single shifts of 12 hours per day (i.e., 12 hours continuous service), with less than 20 starts per hour and all starts will be carried out with an empty drum. The operating environment is quite dusty.

Assignment Requirements

Shaft Material

The initial expectation is that the shaft will be made from high quality shaft ground stock, of Su 350 to 500 N/mm2 grade. You will need to reference a suitable grade that you have selected. The shaft is initially expected to be a parallel sided cylinder bar (no steps).

Core Assignment Requirements: You are to prepare an EXCEL spreadsheet for an engineering manager, showing step by step how you have arrived at:

• Design a suitable shaft diameter using only two analysis methods covered within the course notes: AS1403, Gerber, Goodman or ASME.
• State the diameter and length of the stock material you are proposing to use to manufacture one off your shaft design and the material property.
• Select a gearbox from the SALA catalogue provided.
• Determine a suitable key between your shaft and the boss on which the chain sprocket is mounted.
• Reference to APA7th or Harvard are to be included in your spreadsheet at each key point. The EXCEL spreadsheet is to be easily read and also serve as a guide for new graduates that will learn from you and extend your design to other applications. Your EXCEL spreadsheet is to be preceded by an executive summary. In it you must specify concisely what you propose to buy and what to make. This summary is not to be a general discussion, but brief and to the point. Higher level managers only read this summary, unless something goes wrong, then the details will be examined.

Additional Design Aspects to be Considered:

• Select bearings and bearing plummer blocks to suit this installation. To do this you must determine the angular misalignment of the shaft at the bearings, to allow bearings and or plummer blocks be selected that can function with that misalignment. Suggest tolerances for the coplanar alignment of the mounting faces for the two plummer blocks, and their deviation from the horizontal.
• Determine the lateral deflection of the shaft at the sprocket and assess its effect in terms of the possibility of the chain not engaging correctly with the sprocket due to the shaft deflection.
• Select V-belts and pulleys to replace the existing chain drive. The centre distance between the shaft and driven sheave is approximately 1200mm and a speed reduction between the main shaft and driven shaft (not visible in Figure 1.0) of approximately 2.0 is desired.
• Discuss whether you would prefer to continue with a chain drive or change the power transmission system to a V-belt drive arrangement.
• Design and produce a detail drawing of the steel frame to deal with the points above on an A3 or bigger size drawing sheet to AS1100.

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